I am thinking of purchasing an older Dodge Ram; the listing on craigslist says that the vehicle is in good condition but the heater core is busted. I'm willing to go without heat/AC till I get around to fixing it but I'm concerned whether or not a malfunctioning/broken heater core would also be dangerous to drive due to overheating?

I'm not familiar with how the heater core links to the rest of the cooling system to know.

2 Answers
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There are two things which can be wrong (that I'm aware of) with the heater core. It can be plugged (not letting coolant through), or it can leak. If blocked, there's absolutely no issue. Drive without heat. If it leaks, you'll need to run your heater hoses in a loop, to bypass the heater core. Basically, you are taking one hose from one side (either intake or discharge) going to/from the pump and looping it back through to the other side. I your case (assuming a V8 318 or 360), one of the hoses connects at the water pump on the driver's side, while the other one connects at the intake manifold, just on the passengers side and behind the radiator hose. I would suggest you just get a piece of hose, other than your existing hoses and run it from one side to the other. This way you do not have to shorten or cut your existing hoses to make this happen. Once this is done, you shouldn't have any issues, other than the lack of heat.

If the core has a hole, and leaks coolant, you most definitely cannot drive it. You will need to bypass the heater core entirely.

Otherwise, if it is blocked, you still need to bypass the core. You don't want to stop the coolant from flowing, or you might as well not have it. This depends on how your core is hooked up though.

If you do buy it, you should probably do a full flush of the cooling system, and get the radiator rebuilt or get a new one. If it is clogged or broken, you might as well get rid of any slime or debris, and you'll have to drain the coolant anyways.